The present invention relates to a device for providing a leak-tight coupling between a flexible tube and a rigid coupling connector having two coaxial components adapted to engage one inside the other. One component is mounted within the interior of the flexible tube and covered by this latter. The other component is mounted externally so as to surround said tube, the end of which is clamped between these two components.
A leak-tight coupling between a flexible tube and a rigid coupling connector is already provided by means of a number of known systems which make use of the general arrangements recalled in the foregoing. In particular, it has already been proposed to construct the coupling connector by means of two members which have a conical profile. One member is engaged within the flexible tube with slight force and the other member is fitted over the first and grips the end of the tube in a sandwich arrangement, both members being interlocked in such a manner as to clamp the tube between them.
A design solution of the type just described, one example of construction of which is illustrated in FIG. 1 of the accompanying drawings, is subject to certain disadvantages, especially when the flexible tube is of material having mechanical characteristics which weaken as a result of stress applied to said tube during use over a long period at high temperature, for example. In this case, the end portion 2 of the tube 1 is in fact force-fitted on the first member 3 of biconical shape which is so designed as to be substantially larger in diameter than the flexible tube. Said tube is thus subjected to tensile stress at the time of assembly and remains stressed throughout the service life of the coupling device. An outer ring 4 having the same profile as the end portion of the member 3 is adapted to cover this latter and is then thrust in the direction of forcible engagement by means of an extension member 5 which is screwed onto a threaded portion 6 of the member 3, thus clamping the end of the tube and securely holding this latter in position. However, if the diameter of the member 3 at the end portion 7 of this latter is practically equal to the nominal diameter of the tube, it is possible by means of a simple calculation based on the known angle of slope of the cone formed by said member to determine the increase in diameter of the tube in the zone 8 of larger diameter; this increase represents a not-negligible elongation in respect of this dimension and a value of stress which rapidly becomes excessive as a function of the modulus of elasticity of the material of said tube. Embrittlement of the tube in the zone of junction between this latter and the coupling connector consequently occurs and is particularly disadvantageous when this latter is employed in any atmosphere at higher than average temperatures.